Photographic silver halide emulsion with increased sensitivity

ABSTRACT

A photographic silver halide emulsion chemically sensitized by a cyclic amino compound containing at least one dialkylsilyl group added to the silver halide emulsion.

United States Patent [111 3,615,631

[72] Inventors Harald Huckmdt 52 0.5. CI 96/120, Cologne-Stammheim; 96/1 2 2 Wolfgang Himmelmann, Cologne- [51] Int. Cl G03c 1/10 tam Wilhelm al Schildgen, {50] Field of Search 96/107, Bergisch-Gladbach; August Randolph, 104, 94 Leverkusen; Erwin Ranz, Leverkusen; Walter Simmler, Odenthal; Hans-Dietrich Reference-5 Ciled 60ml, cologne-siammhflm, all UNITED STATES PATENTS Germany [2!] Appl No ,9 3,471,296 l0/l969 l-luckstadt et al 96/107 [22] Filed 1 9 Primary Examiner-William D. Martin [45] Patented Oct 26 1971 Assistant Examiner-Theodore G. Davis [73] Assignee Agfa-Gevaert Aktiengesellschaft Y "y and Hui-Z Leverkusen, Germany [32] Priority Dec. 22, 1967 [33] Germany [31] P15975113 [54] PHOTOGRAPHIC SILVER HALIDE EMULSION ABSTRACT: A photographic silver halide emulsion chemi- WITl-l INCREASED SENSITIVITY cally sensitized by a cyclic amino compound containing at 7 Claims, No Drawings least one dialkylsilyl group added to the silver halide emulsion.

The invention relates to photographic silver halide emulsions chemically sensitized by the addition of cyclic amine compounds containing at least one dialkylsilyl group.

A number of methods have been described for improving the sensitivity of photographic silver halide emulsions other by optical or spectral sensitization through the incorporation of certain sensitizing dyes in the emulsion. The incorporation of such dyes in the emulsion increases the optical or spectral range of sensitivity, and for this reason such dyes are commonly referred to as optical or spectral sensitizing dyes. Contrary to such optical or spectral sensitizers the so-called chemical sensitizers are believed to react with silver halide to form, on the surface of the silver halide grain, sensitivity specks the chemical nature of which depends on the kind of the chemical sensitizer. The sensitivity of silver halide emulsions can be increased by chemical ripening or afterripening during the preparation of the emulsion, by either prolonging the ripening time or by the addition of suitable substance such as compounds of noble metals or thiosulfate or other sulfur compounds. According to another method customarily employed the sensitivity of a photographic emulsion can be increased by the addition of development accelerators or chemical sensitizers to the emulsion usually when it is completely ripened.

Suitable development accelerators are, for example, compounds containing onium groups (for example, quaternary ammonium or phosphonium and ternary sulfonium salts) and polyalkylene oxides and derivatives of polyalkylene oxides.

The process of chemical sensitization, however, reaches a limit beyond which further addition of sensitizing compounds or of prolonged digestion in the presence of a sensitizer, merely increases the undesired fog of the photographic emulsions.

In particular with respect to polyalkylene oxide sensitizers, many attempts have been made to increase the sensitizing action by modifying the chemical structure or by using them in combination with other compounds. However, in practice, none of these compounds completely meet the requirements as regards producing a satisfactory increase in sensitivity without concomitant increases in fog or poor keeping qualities.

It is an object of the present invention to provide chemical sensitizers for photographic silver halide emulsions. Another object is to increase the sensitivity of ordinary photographic silver halide emulsions without concomitant increases in fog or poor keeping qualities to a degree which might seriously affect the usefulness of the emulsion.

We now have found that excellent increases in sensitivity can be achieved with little or no fogging by addition of cyclic amino compounds containing at least one dialkylsilyl group to silver halide emulsions.

Suitable compounds include those of the following formula:

wherein represents: Z oxygen or the group NRI;X a methylene or a dial- R" an alkyl group containing up to six carbon atoms, the compound containing at least one dialkylsilyl group, in particular a dimethylsilyl group.

Particular utility is exhibited by the following compounds:

I. OH;

N-CHa II. CH

III. CH

IV. OH; OH;

Ego-N N-CH;

VI. 0H3

VII. CH3 CH3 The preparation of these compounds is described in Chemische Berichte 94, (1961), pp. 1585 -l59l and 96, (1963), PP. 349 -356.

Those substances which are used according to the invention and which are silamorpholines (7=0) are stable to hydrolysis. Silapiperazines (7= NRL), which may also be used are less stable to hydrolysis and presumably, if they are used their hydrolysis products are also effective.

The compounds according to the invention can be used in any silver halide emulsions. Silver halides which may be used are silver chloride, silver bromide or mixtures thereof, if desired with a small amount of silver iodide of up to 10 mols percent. The silver halides can be dispersed in the usual hydrophilic compounds, for example, in carboxymethyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, alginic acid and its salts, esters or amides, and preferably in gelatin.

The preparation of photographic silver halide emulsions includes 3 separate steps:

1. emulsiftcation and physical ripening which is also called Ostwald ripening;

2. the freeing of the emulsion of excess water-soluble salts, usually by washing with water and drying, and

3. the afterripening which is also called chemical ripening to obtain increased emulsion speed or general sensitivity.

The sensitizer of the present invention can be added to the emulsion before, during or after the chemical ripening or they can be added immediately prior to the casting. In many cases it has proved advantageous to add the chemical sensitizer of the present invention before or during the afterripening.

The particular quantity of the sensitizers of the invention used in a given emulsion can vary, depending upon the effects desired, the silver content of the emulsion, the silver halide composition etc. The amount used is also dependent upon the particular state at which the sensitizer was added during the preparation of the emulsion. Generally they are added in amounts of 0.005 to 5 g. preferably 0.05 to 1 g. per liter of emulsion ready for casting.

The sensitizers can be dissolved in water or a solvent miscible with water or a mixture of water and water miscible solvents, and added in such form to the emulsion. The solvent is not critical and should be selected so that it should have no harmful effect on the photographic properties of the silver halide emulsion.

The optimum amount for any sensitizer of the present invention can be determined for any particular emulsion by running a series ofcomparison tests in which the quantity of the sensitizer is varied over a given range. Exposure of the emulsion containing the sensitizer in a manner well-known and measuring of the sensitivity in conventional apparatuses will reveal most advantageous concentrations. Such technique is well understood by those skilled in the art.

The photographic emulsion in which the sensitizers according to the invention are used, can contain additional chemical sensitizers customarily employed. They can be sensitized, for example, with sulfur compounds as referred to, e.g., in the book The Theory of the photographic Process, by Mees (I954).Pages 149-161.

The emulsions can also be chemically sensitized with salts of noble metal such as gold, ruthenium, rhodium, palladium, iridium and platinum, used in amounts below that which produce any substantial fog. Representative compounds are ammonium chloropalladate, potassium chloroplatinate, potassium chloroaurate, auric trichloride and the like. The emulsions can be sensitized with reducing agents, stannous salts or polyamines and the like.

According to a preferred embodiment of the invention, the spirocyclic quaternary salts are used in combination with chemical sensitizers of the polyalkylene oxide type. Suitable compounds of this type are, for example, those of the following formula:

R-O---OH -OH -DR ..v f wherein R denotes a hydrogen atom or an alkyl group with preferably up to 18 carbon atoms such as an ethyl or dodecyl, an acyl group, preferably an acyl radical of an aliphatic carboxylic acid having up to 18 carbon atoms such as lauric acid or oleic acid, or an aryl group such as phenyl or pdodecylphenyl;

n an integer between 8 and 200. The ethylene oxide groups CH .CH- ..0 may be substituted for instance wit alkyl having up to 18 carbon atoms. Molecular weights of from 1,500 to 10,000 are preferred for the polyethylene oxides. examples of which are described in U.S. Pats. Nos. 2,240,472 and 2,400,532.

Other suitable chemical sensitizers are derivatives of phosphoric acid which contain polyalkylene oxide chains. Suitable products have been described in British Pat. Nos. 1,045,183 and 1,045,184 or French Pat. Nos. 1,396,860 and 1,423,680.

Such compounds are condensation products of spirocyclic pentaerythritol-di-phosphoric acid monohalides and polyethylene glycols containing about three to 100 ethylene oxide units in the molecule. They correspond to the following formula:

wherein R a hydrogen atom or an alkylene oxide chain having 3 to 100 alkylene oxide units;

m an integer from 3 to 100 and Y an integer from 1 to 10.

This group of chemical sensitizers also include the condensation products of amidophosphoric acid derivatives and polyethylene glycols of the above-mentioned type. Such compounds are represented by the following formula:

wherein R a hydrogen atom, an alkyl, aryl or aralkyl group and R an alkyl, aryl or aralkyl group;

R and R may together represent the ring members required for completing a 5- or 6-membered heterocyclic ring;

in is an integer between 2 and 100 preferably between 3 and 50;

p an integer from 0 to 100 and q an integer from 1 to 5.

The spirocyclic quaternary salts according to the invention may also be used advantageously in combination with the cross linked or noncross linked water-soluble quaternated products of tertiary polyamines with bifunctional polyalkylene oxide derivatives. These quaternated products have been described in German Pat. application A 50 5 lXa 57 b.

The accelerators according to the invention may also be used in combination with the morpholine or thiomorpholine derivatives described in French Pat. Nos. 1,506,230 and 1,548,191. The accelerators described in the published Dutch applications 6,614,230 and 6,711,152 are also highly effective.

Furthermore, the emulsions may contain stabilizers such as homoopalar or salt-type compounds of mercury which contain aromatic or heterocyclic rings (e.g., mercaptotriazoles), simple mercury salts, sulfonium-mercury double salts and other mercury compounds. Other suitable stabilizers are azaindenes, preferably tetra of pentaazaindenes, especially those substituted with hydroxyl or amino groups. Such compounds have been described by Birr, Z.Wiss.Phot, 47, 2-58 (1952). Other suitable stabilizers include heterocyclic mercapto compounds such as phenylmercapto-tetrazole, quaternary benzthiazole derivatives and benztriazoles.

The emulsions may also contain optical sensitizers such as the usual polymethine dyes such as neutrocyanines, basic or acid carbocyanines, rhodacyanines, hemicyanines, styryl dyes and oxonoles. Examples of these sensitizers have been described in the work by F. M. Hamer The Cyanine Dyes and related Compounds, Interscience Publishers (1964).

The emulsions may be hardened in the usual manner, for example, using formaldehyde or halogen-substituted aldehyde which contain a carboxyl group, e.g., mucobromic acid diketones, methane sulfonic acid ester and dialdehydes.

The sensitizing compounds the synergistic combinations mentioned are not confined to black-white emulsions but also show similar desirable effects in color photographic emulsions containing color couplers. In this connection it is noteworthy that only negligible fog occurs when used in color-photographic silver halide emulsions which are particularly liable to fogging.

EXAMPLE l To a silver iodobromide gelatin emulsion which contained 60 g. of silver in the form of silver halide per liter, which emulsion had a silver iodide content of 6 mols percent were added:

600 mg. of saponin as wetting agent,

200 mg. of 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene as stabilizer and ml. of a 10 percent aqueous solution of formaldehyde. 75 ml. of a 0.1 percent methanolic solution of the blue sensitizer of the following formula:

The emulsion is divided into 24 equal parts and the substances shown in the following table are added per liter of emulsion to the individual samples. The emulsions are applied on a cellulose triacetate support and the layer is dried.

It is exposed in a sensitometer customarily employed in the art behind a gray step wedge and developed at C. for 10 minutes in a developer of the following composition:

Sodium sulfite anhydrous 100 g. p-monomcthylaminophenol 2 g. hydroquinone 5 g. borax 2 g. make up to l liter with water.

Table 1 The results of the sensitometric measurements are summarized in table 1 below.

Sensitizer Quantity Relative 7 Fog g.lkg. of emulsion sensitivity in om control 0.79 0.05

control 0.70 0.05

control 0.67 0.05 V 0.1 +3.4 0.70 0.05 V 0.3 +2.5 0.72 0.06 V 1.0 +1.9 0.70 0.10

control 0.73 0.05 V1 0.1 +0.5 0.70 0.05 V1 0.3 +1.0 0.70 0.05 V] 1.0 +2.1 0.67 0.05

control 0.7! 0.04 111 0.l +0.8 0.77 0.04 III 0.3 +1.4 0.72 0.04 111 L0 +2.3 0.71 0.05

control 0.86 0.07 [V 0.4 +2.0 1.00 0.10

control 0.86 0.07 Vll 0.4 +2.0 0.87 0.10

' control 0.73 0.05 N-(B-hydroxy- 0.1 :0 0.78 0.05 ethyl)-morpholine (as com- 0.3 10 0.78 0.06 parison to ll) 1.0 -'0.6 0.75 0.07

EXAMPLE 2 sodium sulfite anhydrous 70.0 g. borax 7.0 g. hydroquinone 3.5 g. p-monomethyl-aminophenol 3.5 g. sodium citrate 7.0 g. potassium bromide 0.4 g.

make up to 1 liter with water.

Fixing is then carried out in the usual manner. Compounds A and B which have the following formulas are used as additional chemical sensitizers:

(A) O-CH; CH -O -O-P\ /C\ P--O(CH CH O)mH L O-CH, CHg-O Jun (B) 32% as;

5 N JH, Br

CG CC H, H: H; H:

Table2 Sensitizer Quantity Relative 7 Fog gJkg. of emulsion sensitivity DlN control 0.53 0.06

sensitizer VIII 0.24 +0.5 0.63 0.06

Vlll 0.24 sensitizer control 0.65 0.06 sensitizer sensitizers sensitizers control 0.59 0.06 sensitizer I sensitizcr control 1.20 0.09 sensitizer B 0.48 +1.0 1.20 0.13 Vl 0.24 +1.0 1.20 0.13

sensitizer control 0.67 0.05 sensitizer sensitizer control 1.25 0.10

sensitizer Vlll 0.24

sensitizer The development time in this series ot'experiments was 16 minutes.

EXAMPLE 3 To a mixed emulsion which is composed of 90 percent of a silver iodobromide gelatin and percent of a silver iodochlorobromide emulsion which has been chemically ripened to a maximum sensitivity in known manner with gold and sulfur compounds are added the following ingredients per liter of emulsion:

g. of l-(3'-sulfo-4'-phenoxy)-phenyl-3-heptadecylpyrazolone as magenta coupler 250 mg. of 1,3,3a, 7-(4-hydroxy-6-methyl)-tetraazaindene as stabilizer ml. of an aqueous 5 percent solution of saponin as wetting agent 2.5 ml. of an aqueous 30 percent solution of formaldehyde as hardener and 45 mg. of the green sensitizer of the following formula The above emulsion is divided into 20 equal parts and the sensitizer shown in table 3 are added per liter of emulsion to the individual samples.

The samples are on a cellulose acetate support and dried.

They are then exposed behind a step wedge and processed in the usual manner. Processing is carried out as follows:

Color-forming development 7 minutes stop bath 5 minutes rinsing 5 minutes bleaching bath 5 minutes rinsing 5 minutes fixing bath 5 minutes rinsing 10 minutes The processing baths have the following composition:

Color-fonning developer Diethyl-p-phenylenediaminc sulfate 2.75 g. 'hydroxylamine sulfate 1.20 g. sodium sulfite anhydrous 2.00 g. sodium hexametaphosphatc 2.00 g. potassium carbonate anhydrous 75.00 g. potassium bromide 2.00 g. make up to 1 liter Stop bath Sodium acetate 30.00 g. acetic acid 6.00 g. make up with water to 1 liter Bleaching bath Potassium ferricyanidc 100.00 g. potassium bromide 20.00 g. acetic acid 4.00 g. make up with water to 1 liter Fixing bath Sodium thiosult'ate 200.00 g. make up with water to 1 liter The color density of the magenta layers was determined with a Macbeth Quanta Log, Model TD 102" densitometer, interposing the green filter into the path of the beam of measuring light.

The results of the sensitometric tests are shown in the following table 3.

Table 3 Sensitizer Quantity Relative 'y Fog g./kg. of emulsion sensitivity DlN control 0.70 0.10

control 0.64 0.18

control 0.45 0.15

control 0.42 0.12

control 0.53 0.14

EXAMPLE 4 The silver iodobromide gelatin emulsion of example 1 is divided into 13 equal parts and the substances specified in the following table, table 4.. are added. The emulsion is applied onto a support and dried as in example 1 and developed for 6 minutes at 20 C. in the developer given in example 2. Sensitizers A and B have the formulae given in example 2.

Table4 sensitizer Quantity Relative 7 Fog gJkg. of Sensitivity emulsion DIN control 0.92 0.21 A 0.480 +2.0 1.13 0.31 B 0.480 +1.5 0.96 0.28 111 0.240 +2.0 0.97 0.24

111 0.240 and A 0.480 and B 0.480 +4.2 1.07 0.28

Vlll 0.120 and A 0.480 and B 0.480 +4.4 1.12 0.26

control 0.90 0.15 A 0.480 +2.0 1.06 0.11 B 0.480 +1.4 0.92 0.10 V 0.120 +1.80 0.97 0.18

V 0.120 and A 0.480 and H 0.480 +3.1 1.10 0.40

Vl 0.120 and A 0.480 and B 0.480 +3.7 1.10 0.30

We claim:

1. A light-sensitive silver halide emulsion which contains a sensitivity increasing amount of a chemical sensitizer of the following formula:

wherein Z represents oxygen or the group NR";

R stands for a saturated or olefinically unsaturated aliphatic group containing up to 18 carbon atoms;

X is a methylene or a dialkylsilyl group;

R" represents an alkyl group containing up to six carbon atoms, the sensitizer containing at least one dialkylsilyl group.

2. The emulsion of claim 1, wherein at least one of the group X represents a dialkylsilyl group, in which the. alkyl groups have up to three carbon atoms.

3. The emulsion of claim 2, wherein at least one of the group X is a dimethylsilyl group. v

4. The emulsion of claim 1, which contains in addition a pogyalkylene oxide sensitizer.

. The emulsion of claim 4, which contains in addition a polyethylene oxide sensitizer of the following formula:

6. The. emulsion of claim 4, which contains in addition a polyalkylene oxide sensitizer of the following formula:

in which R represents hydrogen or an alkylene oxide chain with 3 to alkylene oxide units, m is an integer of between 3 and 100 andy is an integer of between 1 and 10.

7. The emulsion of claim 4 which contains in addition an onium compound of the following formula: 

2. The emulsion of claim 1, wherein at least one of the group X represents a dialkylsilyl group, in which the alkyl groups have up to three carbon atoms.
 3. The emulsion of claim 2, wherein at least one of the group X is a dimethylsilyl group.
 4. The emulsion of claim 1, which contains in addition a polyalkylene oxide sensitizer.
 5. The emulsion of claim 4, which contains in addition a polyethylene oxide sensitizer of the following formula: in which R represents hydrogen, alkyl group containing up to 18 carbon atoms, acyl radical of an aliphatic carboxylic acid containing up to 18 carbon atoms or a phenyl group and n is an integer of between 8 and
 200. 6. The emulsion of claim 4, which contains in addition a polyalkylene oxide sensitizer of the following formula:
 7. The emulsion of claim 4 which contains in addition an onium compound of the following formula: 